stewart



June 1, 1948. D, STEWART 2,442,384

FIRE CONTROL COMPUTER HAVING NONUNIFORM TARGET FLIGHT COMPENSATING MECHANISM Filed March 17, 1943 l3 sheetsrsheet 1 ENVEJMTODQ .i $126007! W Z GMM C QTTO g gys- D. J. STEWART 2,442,384

13 Sheets-Sheet 2 June l, 1948.

FIRE CONTROL COMPUTER HAVING NONUNIFORM TARGET FLIGHT COMPENSATING MECHANISM Filed March 17, 1945 a a a z m a 5 a 7 q 2 a. a 9 6 9 r J 2 3 0 8 I m w x w a Na ma a 2% r y %5 2, 22 w z 2 a a 2 2w 1 7s 9 0 G. 4 w% W s m .f. o o a 1 a o 02 5. 1 Mm 0 a T z 23 a E H. vU m L. c 2 z 8 8 w z fi wfl m m N 9 we? .4 w z 3 M 0 5 f w w 7 m w o 8 a C I W o M O m w W a 32 o i Q G .4. DP, 9 m 2 6 35 s I 2 a w a 4 m I 6 a 2 a 4 K 7 2 8 3 K 3 2 3 2 2 9 |l|li||iI1 111---}! i m I ll lllllilllllllllllllll lllil m we. a 8 B mm w a 2 a 4 M W m w 6 w 7 a 6 5 A w 4 a "w 4 c c m. {3 I e 4 3 2 99 a9 a e 0 6 A/ %9 9 M Z o 9 4 we 5 22 2 a 3 9 s4 4? 4 T w. o 2 I "c w M? mw x o m w 444 H 7 i 9 o P a M l 5 c c o 5 8 5 9 2 7 0 '3 M. 5 c M v 4 O w w y M A. v ll c 8 P. w 6 .2 2 2 s 2 o 5 W m 3 m3 6 z 3 3 4 4 w "w %5 M w a W 4 M 4 3 4 4 w a June 1, 1948. D. J STEWART 2,442,384

FIRE CONTROL-COMPUTER'HAVING NONUNIFORM TARGET FLIGHT COMPENSATING MECHANISM Filed March 17, 1943 13 Sheets-Sheet 3 Dun can (7 Stewart June 1, 1948. J STEWART 2,442,384

FIRE CONTROL COMPUTER HAVING NONUNIFORM TARGET FLIGHT COMPENSATING MECHANISM Filed March 17, 1943 13 Sheets-Sheet 4 mflaw T" y J1me 1948- D. .1. STEWART FIRE CONTROL COMPUTER HAVING NONUNIFORM TARGET FLIGHT COMPENSATING MECHANISM Filed March 17, 1943 15 sheets sh eet s I NV EINTQQ i tewarf' D. J. STEWART FIRE CONTROL COMPUTER HAVING NONUNIFORM TARGET FLIGHT COMPENSATING MECHANISM l3 Sheets-Sheet 6 I Filed March 17, 1943 vwi mop Duncan c7 Stewart A fuel,

D. J. STEWART FIRE CONTROL- COMPUTER HAVING NONUNIFORM June 1, 1948.

TARGET FLIGHT COMPENSATING MECHANISM l3 Sheets-Sheet 7 Filed March 17, 1945 wvrs ml'ropd Duncanoi Siewart fall June 1, D. J. STEWART FIRE CONTROL COMPUTER HAVING NONUNIFORM TARGET FLIGHT COMPENSATING MECHANISM Flled March 17, 1943 13 Sheet -s 8 TOn DL/fifian cy Ql I-Ys June 1, 1948. D. J. STEWART 2,442,334

FIRE CONTROL COMPUTER HAVING NQNUNIFORM I TARGET FLIGHT COMPENSATING MECHANISM Filed March 1'7, 1943 v l3"Sheets-Sh eet 9 f fluncan Q1 tewart- A7 12,1 W,MM

June 1, 1948. D. J. STEWART 2,442,334

FIRE CONTROL COMPUTER HAVING NONUNIFORM TARGET FLIGHT COMPENSATING MECHANISM June 1, 1948. D J, STEWART FIRE CQNTROL- COMPUTER HAVING NONUNIFORM TARGET FLIGHT COMPENSATING MECHANISM Filed March 17,. 1943 13'Sheets-Sheet 11 NVE'N T OL- Duncan CM fitewart- 4, P 6M4. (7" ,7

oq -rom g June 1, D. J. STEWART FIRE CONTROL COMPUTER HAVING NONUNIFORM TARGET FLIGHT COMPENSATING MECHANISM Filed March 17, 1945 15 Sheets-Sheet 12 NVENTOQV' Duncan 0/. Stewart June 1, 1948. D. J. STEWART 2,442,384

FIRE CONTROL COMPUTER HAVING NONUNIFORM TARGET FLIGHT COMPENSATING MECHANISM Filed March 17, 1943 l5 Sheets-Sheet 15 mob Duncan Cy tewam & P W v TToa lg-ys Patented June 1, 1948 FIRE CONTROL oomUTER 'HAVILNG NON- UNIFORM TARGET FLIGHT COMPENSAT- ING MECHANISM Duncan J. Stewart, Rockford, Ill., assignor to Barber-Colman Company, Rockford, 111., a corporation of Illinois Application March 1'7, 1943, Serial No. 479,431

13 Claims.

The invention pertains to the art of predicting the future position of a moving object or target so that the prediction may be used in controlling the firing of a projectile to intercept the target.

Predicting systems usually operate on the assumption that the target being observed is traversing and. will continue to traverse a straight path at constant speed. Accordingly, any departure from such path or non-uniformity in velocity up to the predicted time of target interception will result in an inaccuracy. The primary object of the present invention is to measure any such departure or inaccuracy and correct therefor.

Another object is to compare the actual position of the target as observed at a given time with the position previously computed for the same time and thereby determine the error in the prediction.

A further object is to make the comparison continuously and modify the current or present prediction correspondingly.

A more detailed object is to keep a record of the measurements of the predicted future positions of the moving target and later compare these with measurements of the actual position of the target at corresponding times.

A further object is to divide the measured correction into parts corresponding to the respective coordinates that locate the target in space.

The invention also resides in the novel character of the mechanism for determining the correction' and the manner of modifying the current predictions.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection wth the accompanying drawings, in which Figure 1 is a schematic view illustrating various target positions in relation to the predicting and projecting apparatus.

Fig. 2 is a similar view illustrating one coordinate system that may be used.

Fig. 3 is a fragmentary perspective view of the main operating parts of the apparatus not including the correcting mechanism.

Fig. 4 is a fragmentary plan view of the main parts of the improved predictor.

Fig. 5 is an enlarged fragmentary perspective view of one of the recorders.

Fig. 6 is a fragmentary perspective view of t e mechanism for driving the record carriers.

Figs. 7, 8, and 9 are schematic views and wiring diagrams of the range, altitude and azimuth rec- 2 ords and the mechanisms for recording and reading the same.

Fig. 10 is a diagrammatic view showing different target positions involved in making the correction.

Fig. 11 is a perspective view similar to Fig. 3 but on a larger scale and including the correcting mechanism.

Figs. 12, 13, and 14 are schematic views and wiring diagrams of the mechanisms for setting and reading the azimuth, altitude and range records of the computed future position and for introducing the corrections.

While the invention is susceptible of various modifications and is applicable to many different kinds of predicting systems, it is embodied for purposes of illustration in the system shown in an application Serial No. 4 15359, filed May 1942, by myself and Howard D. Colman to which application reference is made for more details. It is to be understood that I do not intend to limit the invention by such exemplary disclosure but aim to cover all modifications, alternative constructions, methods and uses falling within the spirit and scope of the invention as expressed in the appended claims.

The general method of prediction as described in the aforesaid application involves tracking a moving target T continuously from a point 0 of observation to measure the values of the separate coordinates that locate the target in its present position B (Figs. 1 and 2), preparing continuous records of the changing values of these coordinates, sensing such records to determine the 0001- dinates of a past position A of the target immediately preceding the present by a known time interval, and from the six coordinate measurements, computing the coordinates of the target in its future position C. A predetermined ratio.

is maintained between the past interval and the interval by which the computed target position C leads the present position B, and this past interval is varied progressively so that the future time represented by distance BC will always be equal to the time required for the projectile to travel from the gun or projector G to the computed position C.

While the foregoing method may be practiced using any desired coordinate system, the polar system is employed in the apparatus to be described herein. That is to say, the present target position is ascertained by measuring the slant range Tb of the target in its present position (distance OB, Fig. 2), the altitude angle 0b, and the azimuth angle b relative to any desired reference line. The coordinates locating the target in the past position A will be referred to herein as Ta, (9a, and (#2. while the predicted coordinates corresponding to the future position C are To, and c.

With the exception of a finder RF for measuring the range coordinate, all of the parts of the predictor are combined in a single unit indicated generally at P and joined by suitable electrical connections by which the coordinate measurements are transmitted from the director to the projector or gun G. The'latter incorporates suitable servo mechanism for quadrant elevation and azimuth angle adjustment, and in the case of explosive projectiles, a fuse setter of well known construction.

Measuring present and past target positions These steps in the above method are carried out by apparatus which is fully illustrated and described in the aforesaid application. To simplify this disclosure, the apparatus is illustrated somewhat diagrammatically and only a general. description will be given using. the same numerals on corresponding parts inorder to facilitate reference to said application for further details.

To measure the presentazimuth and altitude coordinates, the target is observed through the eye pieces 25 and of telescopes (Fig. 3) 24 and 55 carried by a horizontal shaft 25 on the upper end of a vertical shaft 34 journaled in the machine frame (not shown). 'One observer turns a hand-wheel 4'6 to follow the motion in azimuth, and'this motion is communicated through the shaft 3 3, a gear 36 thereon, and a gear 31 to a gear 38 on a vertical sleeve 22 (Figs. 3, 4, 7, 8, 9, and-11) which is thus positioned angularly in accordance with the present azimuth.

The other observer turns a cranl; 52 (Fig. 3) to follow the target in altitudeand this motion On one side of the loop, rollers 95 (Fig. 5) on the chain links mesh with sprockets I26 which are driven at a constant speed by a motor I29 (Figs. 4 and 6) to advance the chain and the lugs IIH at constant speedpast a recording position I24 (Fig. 9). At this point the successive lugs pass between the walls I48 and I49 of a j notch I41 (Fig. 5) in a setter I25 which is mount- I39, the lugs are .cammed toward the notch I41 is transmitted through-a sleeve 53 to a difieren tial 6i which subtracts the component due to the azimuth motion so that the intermediate gear 23 (Figs. 3, 4, 8, 11, and 13) of the differential turns back and forth with changes in the target elevation and thus indicates the true. altitude angle 0b.

The range as measured by the finder RF is transmitted electrically toa selsyn receiver 67 (Fig. '7) which actuates switches 14' and I5 that control a followup motor- 72 and cause'a shaft 2i (Figs. 3, '7, 11, and 14) to be positioned an.-

gularly in accordance with changes in present range Tb.

'As a preliminary to ascertaining the coordinates of the target at the selected past time, position A, separate mechanical records are prepared of the present coordinates as set up on the present coordinate 'indicatc'rsZI, 22, and23. In the present instance, each record comprises a succession of mechanical elements or lugs I95 (Fig. 5) arranged in one or more rows that extend longitudinally of a flexible carrier in the form of an endless fiat loop of chain comprising a series of pivotally connected links 94 and connecting pins 95 extending around spaced rollers I23, the latter being slidable vertically in guideways III. The links carry bars '91 having channels 98 extending edgewise of the chain and constituting guides for individually adjustable cars I28 with which the control lugs IOI are rigid.

The major parts of the chains and. their setters and sensers are numbered correspondingly, the exponents z and 22 being used to designate the parts of the azimuth record and exponents 1" and. a for the range and altitude records respectively.

ed on a bar I33 to move laterally of the chain. The lugs I! are shifted at the setting position,

and beyond the: setter the row becomes shaped.

in accordance with the changes in the position of the setter I25; By means of a swinging guide as they approach the setter. While in control of the setter the cars I00 are locked frictionally in the grooves so that the positions are retained until"the" lugs have passed va senser I89 (Figs. 4 and"? to 9) on the opposite side of the chain loop after which the clamping force is released to free the cars. I k

Each senser I is movable edgewise of the chain and has pivoted thereon a feeler or shoe I98 (Figs. ,7 to 9)- which bears against the chain lugs IIH passing the sensing position NH and actuates control switches 204 and 295 in accordance with changes in the edgewise position of the lug then in activeposition. The senser is spaced from the setter a distance corresponding to the past time interval above referred to and represented by the distanceAB (Fig; 1). Toena'ble this interval to be varied as above described, the chain meshes adjacent the senser with sprockets I82 (Fig. 6) which are ona shaft I83 and driven at a speed varied automatically in accordance with the computed time of projectile flight represented by the distance 00. To this 'end, the shaft is driven from the intermediate gear I86 of a differential I81 having one terminal driven by the constant speed chain drive motor I29 and the other terminal driven intermittently. as will appear later, in accordance with changes-in the time of projectile flight; 7

The chain 9I (Figs. 5 and 9) on which the changing values of present azimuth are recorded has two rows of control lugs IIlI and I0 I which are set to form the azimuth record 81. The range andaltitude chains 92 and 93 (Figs. 7 and 8) each hayeone row of'lugs "I-IlI and IIlI respectively, these being adjusted'to form the range and altituderrecords 88 and 89.-

To set the-control lugs I0 I in accordance with the true value of the present altitude, the setter slide I 33 (Figs. 4 and 8) is shifted back and forth with changes in the angular position of the altigear 23.

In a similar Way, the slide I33 is moved in unison with the range indicator; or shaft 2 I. The connection (Figs. fl and '7) is through idler gears I66 of the same size, the terminal one meshing with rack teeth on theextended end of the slide I33 The row of fingers I'DI. beyond the setting line I24 is ihclined as shown inFig. '7 in response to a progressive increase in. the range coordinate and would be inclined reversely when the value of the range coordinate is decreasing.

To permit of an unlimited motion of the target tracking mechanism-in azimuth, the azimuth rec- 0rd 87 is set up in two parts on the lugs IIII and ItII b cams I68-ancl IiESXFigs. 3', 4, and -9) each having successive inclines of reverse slope. With this cam arrangement, the two rows of lugs Illl and, H11" are set in identical patterns although they are shifted relative to each other longitudinally of the chain by an amount corresponding to the angular displacement of the cams I68 and 169 relative to each other, both followers I14 and H5 for these cams moving along the same radial line. It will be observed that the control lugs H and Ill I forming the spaced subdivision a, and a of the two cam patterns are set by the cam. surfaces 110 and ill respectively and that within the length 17 in which the subdivisions overlap, they have the same inclination. The rows produced by the corresponding cam inclines will be inclined reversely during counterclockwise rotation of the disks so that a reversal in the direction of the azimuth change is evidenced by a reversal in the slope of both rows of lugs Hil and 101.

From the coordinate records 87, 83 and 89 prepared as above described, it is possible to locate the second point A and thus determine the line of flight L as well as the distance between the points. This is accomplished by sensing the traveling records continuously and simultaneously at the points It! above referred to, setting three indicators in accordance with the azimuth, range and altitude coordinate values a, Ta, and 93. thus sensed. Herein, the azimuth and range indicators are constructed the same as the present indicators and comprise a sleeve Ill (Figs. 3 and 9) which is positioned angularly according to the true value of the past azimuth and a shaft I18 (Figs. 3 and 7) for past range. A shaft [l9 (Figs. 3 and 8) is adjusted angularly according to the altitude of the target in the past position A.

The past range indicator or shaft H8 is actuated by a follow-up mechanism 224 (Figs. 3, 4, and '7) whose reversible electric motor 225 is controlled selectively by the switches 2M and 295 which are positioned by the shoe I98 of the senser IBB The past altitude indicator I19 is actuated in a similar way by a follow-up mechanism 228 (Figs. 3, 4, and 8) including a motor 229.

Referring to Figs. 3 and 9, the azimuth indicator or sleeve ill is constructed and mounted in the same manner as the present azimuth indicator 22. Keyed to this sleeve is a gear 232 meshing with a gear 233 on the slow speed shaft 234 of a follow-up unit 235 having a motor 236. Because of the different way of recording the azimuth coordinate, the motor is controlled in a different manner. The subdivisions a and a of the divided record 81 are used alternately in controlling the motor to cause the past indicator to follow the movements of the present indicator but at a later time. Thus, the control lugs I01 and I I" coast with inclines 231 and 238 on cam disks 239 and 24!] which inclines are duplicates of the inclines Ill and Ill on the disks I68 and [69. The disks are fast on the azimuth indicator IT! and are engaged along the same radial line by followers 243 and 244 which are carried by the slides. I9 and I94 of the azimuth sensers I80 and I86 and therefore impart the proper follow-up motions to the control switches.

To utilize the subdivisions a and a of the azimuth record alternately, switching means is provided for transferring the control of the motor 236 from the switches 2f! and 205 to 2M and 2435. and vice versa. The transfer is made .in response to movement of the past indicator I11 and within the overlap b of the different record subdivisions during which time the position of the indicator, as determined by the joint action of the lugs It'll and one incline 231, will be identical with the indicator position as determined jointly by the lugs In!" and the active cam incline 238. The transfer is effected by inclines 241 and 248 alternating in angularly spaced relation around a disk 246 and acting on a follower 249 on a shaft 250 which carries an arm 25| disposed between two spring contacts 252 and 253 cooperating with a stationary contact 254 to form two switches 255 and 256'.

With the parts conditioned as shown in Fig. 9, the switches 2M and 295 and the control lugs llH are in control. In response to closure of one switch 2H5 by a change in the position of one of the control lugs Ill! passing the reading position ISI, as shown, the motor 236 is operated to turn the azimuth indicator and the cams 239 and 240 clockwise. Reverse turning of .the disk and indicator occurs when the other switch 2% is closed in response to a reversalin the slope of the line of lugs it! passing the sensing shoe I33". If there is no change in the past azimuth, the passing lugs Illl will parallel the chain path and both switches will remain open and the motor 236 will be idle. As in the case of the other readers, the shoes i533 and I98 are pivoted on the ends of the switch arn1s2ill and 2G I which in turn are pivoted intermediate their ends on the slides I95 and I94, thelatter being the followers of the follow-up cams 235i and 228. With this arrangement, theefiective position of each shoe is determined by the position of the lug Ifll engaging it at the reading position 5!.

Computing coordinates of future target position In the exemplary prediction, the coordinates of the present and past target positions as' set up in the six indicators 2|, 23, 22, Ill, [UL-and H9 are combined by geometrically representing in miniature the present and past target positions A and B, locating on a line L through these positions a point corresponding to the future position C, and measuring the coordinates of the latter point. The computer comprises generally three arms 28L 262, and 263 (Figs. 3, 7, 8, and 9) of variable lengths swingable about vertical and horizontal axes intersecting fixed points 0, O, and O" which are spaced apart short distances 2 along a straight line, the arms being pivotally connected at their free ends a", b, and c to a bar 3 I l which maintains the points in a straight line and variably spaced so that the distance a"c bears a fixed ratio, 3 in this instance, to the distance a"b'. The fixed pivots are spaced in the same ratio, that is, OO"/O'O equals 3. The arms and the bar 3|! form a linkage system which operates mechanically to adjust the length and position of the arm 23! and the point 0 in accordance with changes in the lengths and angular positions of the arms 262 and263.

The points a and I) represent in miniature the past and present target positions as defined above and are positioned in space and relative to their pivots O and O" in accordance with measured coordinates of these target positions.

The motion of the present range indicator 2| is transmitted to a. pinion 287 (Fig. 3) meshing with rack teeth on the arm 232 so that the latter is lengthened and shortened in accordance with the changing values of the present range re. The connection from the register 2| is through a differential 3&4, a gear 382, a shaft 299 concentric with the azimuth indicator 22 and gears 297, 298, a differential 294, and gears 293, 292, 290, and 289 to the pinion 281.

To tilt the arm 262 in? altitude, a yoke 212 carrying the arm is'tilted through a connection extending from the gear 59 through gears 60 and 219, a shaft 280, gears 28!, 282 and 284 to "a bevel gear 286 rigid with the yoke. The

yoke '212 and the sleeve carryingthe pinion 281.

are supported on a frame 215 keyed to the aziinuth indicator 22 so that the point of b turns in azimuth with this indicator.

Similar connections, the parts of which are indicated by corresponding reference numerals with the addition of the exponent a, are provided for positioning the arm 263 in accordance with the values of past range, past altitude and .past azimuth as set up on the indicators I11, I18, and I19.

The point I) is rig-id with the bar 311 and the points a" and-c are carried on slides 3|9 and 320 (Fig. 3) connected to racks 336 and 339 which mesh respectively with a pinion 335 and a gear 334 rigid with each'other. This connection maintains the proper ratio in the spacing of the points a, b and '0.

With the linkage system constructed as above described, it will be observed that the ball 268 "or point will be moved in accordance with "changes in the lengths and inclinations of the present and past position arms 262 and 263 while the ratio a"c/a"b' is maintained fixed. The points 0;", b and c are of course always maintained in a-straightline. Accordingly, the movements'of the points a" and b, which represent in miniature the past and present target positions, are utilized through the medium of the pantograph system to combine the present and past coordinates as recorded on the indicators and thus computeores'tablish the location of the point e which represents the future or predicted target "tosiuon.

Toascertain the azimuth, range and altitude coordinates of the computed future target position, the future arm 26I is adjusted in length and position in response to changes in the position of thepoint'c, and these adjustments are communieat-ea "to shafts 355 and 356 and a sleeve 351 (Figs. 3, 7, 8,9, 12, 13 and 14) which constitute respectively the indicators for the future range, futurealtitude and future azimuth coordinates toyin and at. These prediction registers and the arm '261 are constructed and mounted on the main frame in the same way as the present and past "registers previously described, and the connections between the arm and the registers are of the"same general construction, the main parts bein'g'indicated by corresponding reference num- =eral'stb"whijch the exponent c has been added.

Instead of making the socket for the ball 266 "rigid'withthearm 26l as in the case oi the arms 262"and 263, 'a "connection is provided which perln'its of relative movement between the arm and socketin three directions respectively correspond- 'g'to the range, azimuth, and altitude movements f'the point 0. The degree of such movement is Eient to permit the actuation of pairs of fractures 39j'a'nd 392, 369 and 31a, and 38l and 382 '(Figs. "7, '8 ands) respectively controlling renew-11p mechanisms "358, '359and 36!] (Figs. 3, -,"'9, 11,12, 13 and 14) by which the future a'z rfifith, altitude, and range indicators and the a'r'in"26'l are'a'ct'uated. I

To th'es'e en-d's'and as-shown more in detail in the aforesaid pending application, the ball socket is rigidwitha le'ver 36l (Fig. '3) proj ectingthro'ugh a h'ole-i'n a tube '362' to which the lever is ipivotally connected"intermediateits ends to swing 3301311. the azimuth indicator oresleeve 351. .result, this .sleeveiw'illbeturned in one direction about an axis 363 parallel-to-the arm 26! and shown diagrammatically inlEig. 9. The tube. 362 in turn projects through a hole in a lever 3'64 and is pivotally connected to the latter by pins 365 which extend perpendicular to the first mentioned axis. The lever 364 is disposed between the lower end of the arm 26| and a bracket 3'61 thereon and is pivoted on a pin 366.

The multiple gimbal joint thus formed provides for three independent motions of the pantograph point 0 relative to the arm 26! and functions to segregate from each other the motions of the point which are due to changes in azimuth, altitude and range. Thus, thelever '364is' swung about the pivot 366 in response to movements of the ball 268 in altitude (Figs. 3 and .8). Such actuation controls switches I369 and 31.0 which govern the operation of the follow-up mechanism 359 to position the future altitude register or. shaft 356 in accordance with the motions of the 'ball 266 resulting from changes .in the positions in points a and I) caused .by changes in the past and present altitude coordinates. The .follow-up motion is transmittedfrom-the shaft 355 through the dii ferential 358, .thegear 394, the shaft28l1",

the gears'ZBI 2252 and 28 1 to the bevelgear 286" which is rigid with the .yoke 212".

Changes in the future range as computed by the pantograph system cause movement or the lever'efil (Figs. 3 and '1) about the pivot 3.65 to operate the switches 38] and 382 and contrblthe reversible motor 385 of the follow-up mechanism 365. This drives the future .rangeindicator shaft 355 which is on one terminal of .a differential 381 whose intermediate gear 388 meshes withthegear 392. The other differential terminal is connected by a gear 31135 to the gear 380 on the azimuthindicator. Thus, the motor 385 operates through gears 3132", 298', 291 (Fig. "3), .the differential 254 and the ,gears 292 290, 289 and the pinion 281 to adjust the length of the arm 26!. In response to closure of either of the switches 138i and 332 following a change in the computed or'future-range, thelmotorl385 runsthe pinion "231' in a direction to lengthen'or shorten the arm 26! .to correspond to such change. The motor stops when :the. follow-up motion imparted totheswitch contacts causes the active switchto be; opened.

Changes in'the futureazimut-h as determined bythe pantograph system cause swinging of the lever'3tl (Figs. Band 9) at right angles to the rangemotiouand about thepivot'3'63. In-t'hese mot-ions, thearm .36! .operatesswitches 391 and 392 controlling :a. follow-up. motor .401 which opcratesthrough. reduction gearing to .drive .a shaft 4-83 carrying agear 502 that. meshes withthe gear As a ortheother-accordingto which of theswitches 351 and 3-92-is closed, and the motion will continue 26! and all of the :parts "fcr'actuating the-same are carried by the frame "215 which in-turn is 1 journaled .in' the :main frame.

:From ithe :Itoregoing, it will The observed that "th linkage system, which-is actuated in -accordence with changes in the present and past 'coordinates, geometrically computes the-future target position as represented in A miniature by the pointicfan'dcontrols the switches by which 'the follow up mechanisms are actuated to "set up the separate indicators and thereby segregate the computed future coordinates.

The motions of the future azimuth indicator 351 may be utilized directly to control the positioning of the gun in this coordinate. This may best be accomplished by providing a Selsyn transmitter 4&5 (Figs. 3 land 9) having its rotor fast on a shaft which carries the gear 386 that turns in unison with the future azimuth register. A Selsyn receiver 404 (Fig. 9) of similar type is energized from the transmitter through the electrical connections above referred to and utilized in the usual way through a power driven servo actuator (not shown) to position the gun continuously so that except for the influence of windage and parallax, the un is always set in accordance with the future azimuth coordinate as com puted by the director.

Quadrant elevation of the gun is determined not only by the computed future altitude coordinate but also by the future range, trajectory, etc. In this instance, it is computed by means of a three-dimensional cam 40! (Figs. 3, 7, and 8), contoured in a manner well known in the art to provide a point on its peripheral surface radially spaced according to the correct quadrant elevation for each different combination of range and altitude. The cam is mounted for rotation in accordance with the changing value of the computed future range and is shifted axially with changes in the future altitude. Its follower, which comprises a ball 498, is mounted on the end of a rack bar 309 guided for endwise movement and meshing with a gear 4H1 on the rotor shaft of re. transmitting Selsyn 4H. Through electrical connections, the transmitter motion is reproduced in a Selsyn receiver 4I2 (Fig. 8) on the gill! carriage and this receiver is utilized to control a servo actuator by which the gun is positioned for the correct quadrant elevation.

The cam 40! is fast on a vertical shaft 4M (Figs. 3, '7 land 3) journaled in the main frame and is turned back and forth with changes in the angular position of the future range indicator 3'55. Herein the connection includes interconnected gears 4 I8 and 4H), a vertical shaft 529 and gears 42 I.

To provide for axiral shifting of the cam idl, a screw threaded portion 423 (Figs. 3 and 8) of the shaft 4 I t carries a nut 424 which is journaled in the main frame and carries a gear 525 meshing with a gear 626. The latter is driven through bevel gears 21, a horizontal shaft 428, and gears 429 and 639, one of the latter being fast on the shaft 356 or future altitude indicator.

The time required for the projectile to travel from the gun IOI other projector to the target in the predicted future position of the latter is also controlled by the future range and future altitude coordinates and computed by a three dimensional cam 434 (Figs. 3, 7, and 8) fast on the shaft 45 l and engaged by a follower The peripheral contour of the cla m is such that the follower occupies a definite endwise position for each combination of future altitude and range which respectively determine the axial and angular positions of the cam. The time of flight thus determined may be corrected. by the dead time mechanism see (Figs. 3 land 4) described in detail in the aforesaid application. The resultant motion is communicated to a Selsyn transmitter .53

(Fig. 4) which in turn is connected electrically to a receiving Se l-syn (not shown) associated with the gun and controlling the fuse setter therefor. For this purpose, the drive shaft 45!! of the Selsyn.

458 is arranged to be driven by a follow-up mechanism 463 (Figs. 3 and 4) including a reversible motor 462 controlled by switches which are actuated by an arm 469 (Figs. 3 and 4.) in response to movement of the time of flight follower 435. In this way, the Selsyn 458 is set in accordance with the computed time of flight combined if desired with a dead time correction of the proper sense and am ormt.

Automatic adjustment of the past time As set forth above, the reversible motor I532 (Figs. 4 and 6) is operated intermittently to vary the speed of advance of the memory chains SI, 92 and 93 past the reading positions I8I, and thereby correspondingly change the length of the m mory or past time interval so as to maintain the fixed ratio between this interval and the ,computed value of the time of flight. Herein, the direction and extent of operation of the motor are controlled by switches 48I and 482, which are formed by contacts on arms 483 coacting with a tongue 484 on a lever 485 pivoted at 486 on a block G8? which is mounted adjacent the slide 451 and guided for movement parallel to the latter. Beyond the pivot, the lever is connected to a pin 259 depending from the slide 441 so that the lever 485 is swung back and forth with changes in the time of ffight as evidenced by movement of the cam follower 435. 7

The block 48'! (Figs. 3 and 6) carries a nut 488 into which threads a shaft 489 connected through bevel gears 49%! and a gear 4! which meshes with the gear I99 driven by the motor I92 and carried by one terminal of the differentialIBl (Fig. 6). Through these connections, the motor I92 acts as a follow-up to position the slide 481 in accordance with the time of flight changes, the differential I87 acting to add or subtract the motor motion to the constant speed motion imparted to the chains by the motor I29. Since the variable advance of the chains in accordance with changes in the time of flight is on the reader sides of the chains, the length of chain between the recording and sensing points and therefore the time interval that elapses before the reading of the records corresponds exactly to one-half the time of flight existing at the time the chain cars are read, not when they are set.

Clorrectzon for non-uniform flight or accumulated errors The method of prediction and the apparatus thus far described forms the subject matter of application Serial No. 445,259 filed by myself and Howard D. Colman and is typical of the various types of predictors to which the present invention may be applied. Except for inherent inaccuracies arising in tracking the target, in converting and transmitting the measurements, or in manufacture, the apparatus, like others that are available, will register an exact prediction when the target is traveling in a straight line and at a uniform velocity; The present invention as covered by the appended claims aims to modify the predicting system first to detect errors in the prediction whatever their cause may be, and then to introduce corrections which will compensate for the errors fully or partially depending on their character. The nature of the correcting action and the wide applicability of the modification will be apparent from the following -example. Assume, for

example, that the target being tracked is movin in a path L' (Fig. 10) lying in a plane through 1'1 the point of observation and having uniform curvature. At the instant the target arrives at B, the director above described will compute the future position C on a line through B and the measured past position A. In view of the curved line of flight, the target actually passes through a point B after the lapse of the computed time of flight. This becomes a new present position which together with a new past position- A' controls the predictionof a new future position C which also deviates from the actual future position B" after the lapse of the computed time of flight from B.

By measuring the senseand extent of the deviation- CB and adding this difference algebraically to the prediction C registered by the director when the target is at B, this prediction will be corrected to locate the target at B", the position which the target will actually occupy following the lapse of the computed time of flight from B, the line of flight changing at a uniform rate.

More particularly, the improved method of correction involves the steps of comparing, either, intermittently or continuously, the values of the measured present coordinates with the values previously computed for a time corresponding to the present, and continuously applying the differences ascertained by such comparison. to the coordinates of the future position as predicted on the basis of the actual present position. The process is continuous 50 that after the target has been followed for one and one-half times of flight, the corrections will compensate for nonuniform flight, and the target position actually measured at any instant will coincide with the previously computed position for that instant provided that the deviation from linear flight continues at a constant rate.

The accuracy of the compensation will, of course, depend on the character of the deviation of the target path from a straight line. In many instances, a correction ascertained repeatedly at relatively short intervals and applied continuously will be satisfactory and has the advantage of simplicity. The application of such a correction involves the provision of devices clutched to the prediction indicators periodically with provision for comparing their positions with those of the present indicators at the end of a time of flight, difference or correction thus obtained being added to the prediction then in control of the gun positioning.

Greater accuracy may be obtained by making the comparison above referred to continuously. This method is illustrated herein and will now be described. It involves continuously recording on separate traveling carriers the values To, 9c, and be of the computed future coordinates as set up on the future indicators 355, 356, and 351, continuously reading these records at a time corresponding to the present, that is, advanced from the recording position by the computed time of flight, and comparing the coordinate values thus read with the present values 1', 0, and being measured and set up in the indi-cators2 I, 22, and 23 whereby to determine the sense and amount of the diiferences that. constitute the corrections to be combined with the repective coordinates of the future target position then being predicted.

Advance of future record carriers.Referring now to Figs. 4, 6, and to 13, the computed future azimuth, range and altitude coordinates are recorded on chains SM, 502 and 503 which are identical inconstruction to the present memory chains BI, 92, and 93. A detailed description is therefore unnecessary, the parts of the chains and the associated devices bearing, the same reference numerals with the addition of the exponent f. The cars and the control lugs IDI IIlI' WI, and IOl of these chains are po sitioned by setters 125, I25 I25", and I25 which are actuated by the shifting of bars I33, [33 I"33 and I33 the lugs coactin-g with sensers I80, I80, and I'Bil which are on slides I'M, IM I94, and I94 The chains are advanced past the recording position 504 by sprockets I26 and past the sensing position 505 by sprockets I82 (Fig; 6). Cams I63 and 2I4 rotatable with the sprockets control the locking and release of the cars I00. The only difference between the present and futurememor chains is that in the latter, the constant speed drive from the motor I29 through the shafts 435, 440 and gears 442 (see Fig. 6) is to the sprockets I32 on the senserside instead of the sprockets I26 on the setter side as with the present memory chains 9|, 92 and 93.

The shafts I211 of the sprockets I2 ii are interconnected by gears 506 (Fig. 6*) and driven through bevel gears 501, av shaft 508, and bevel gears 569 from one shaft I83 which, as previously described, is driven through the difierential I81 so as to respond to the combined motions of the constant speed motor I29 and the motor I'92 which is operated intermittently and selectively in opposite. directions in accordance. with changes in the computed time of flight. Since the drive motions from the shaft .439 to the shaft '0 (Fig. 6) andifrom the shaft 5H8 to the first shaft I2"! are reduced in a 1 to 2' ratio by the gears 442 and 501, the future chains will be advanced at one-half the speed of the present chains and with the same spacing of the setting and reading positions 504. and 505' (Figs. 12, 13 and 14), the interval between these positions equals the time of flight instead of one-half the time of flight as in the case of the present memory chains.

With the arrangement thus employed, the .position of each. chain car passing the sensing point corresponds to the coordinate value at a time prior to thesensing time by an amount equal to the time oi'flight at the time the particular chain car was. set. As a result, the future memory chains provide a continuous record of the previously computed target position corresponding to the present time.

Azimuth; correction.By comparing Figs. 9 and 12, it will be seen that the future azimuth coordinates are set up on the chain 501 in the same way that the present coordinates are recorded on the chain. 9 I. The bars I33 and [33 of thesetters I25 and t25 are actuated by cams I68 and H59 (Figs. 11 and 12) which turn with the futureazimuth indicator or sleeve 351. Thus, the rows of control lugs MI and IIJ'I are shaped in accordance with the cam patterns and the changes in computed azimuth so as to form traveling records of this coordinate.

At the sensing position 505, the control lugs on the cars actuate shoes I 98 and I88 of sensers ItIl and t8!!!" to position switches 204, 20.5", 2M and 2H5 and control the reversible motor 5 of a follow-up unit 5112 (Figs. 11 and 12) which through appropriate reduction gearing turns a shaft 5I3 which carries a gear 5M meshingwith a gear 5I5 with which cams 239 and 240 rotate. These cams are of the same shape as the setter cams Hi8 and I-69 and their followers are on the slides I94 and Him 13 through which the switches 204, 205, 294 and 205 are actuated to control the follow-up action so that the gear I5 is turned back and forth with changes in the computed future azimuth asread. A cam 245 rotatable with the cams 239 and 240 actuates an arm 25I and switches 255 and 255 to transfer the control of the motor 5II from one set of switches to the other so that the motion imparted to the gear 5I5 duplicates that of the future indicator 35? but later by an interval equal to the time of flight. Thus, the shaft 5I3 turns in accordance with the azimuth of the computed present position of the target and constitutes the indicator for the computed present azimuth.

To compare this computed azimuth with the actual present value b, the gear M4 on the indicator 5I3 drives a gear 5I6 connected to one terminal member of a difierential 5H having its other terminal member driven by a gear 5 I B from the gear 36 which is positioned angularly in accordance with the actual present value of the azimuth coordinate as it is measured by tracking the target. If the target path is a straight line, the actual and computed values will be the same, and the intermediate gear 5| 9 will occupy a neutral position in which no correction will be added. If however, the computed and actual values differ, for example, because the target is traversing a curved path, the intermediate 5I9 will move away from such position in a direction and by an amount corresponding to, the deviation. Of course, the corrections are small so that a lever might be used instead of the differential gearing in making the comparison.

The correction thus determined is added algebraically to the computed value of the azimuth coordinate as transmitted to the azimuth Selsyn 405 from the future azimuth indicator 351. To this end, one terminal of a differential 525 is driven through a gear 52! from the gear 389 on the future azimuth indicator 351, and the other terminal carries a gear 522 driven by gears 523 from the intermediate gear 5I9 of the comparing differential 5H. The intermediate 524 of the differential 529 drives the gear 386 of the azimuth Selsyn 4115.

Range correction.-Referring to Figs. 11 and 14, the rack bar I33 for positioning the setter I25 to record the computed future range on the chain 502 meshes with and is shifted back and forth by a gear 525 on a shaft which is driven through gears 526 from the shaft 355 which, as previously described, is positioned angularly to indicator the future range as computed by the director. The control lugs I lll of the chain cars IIlIl -f thus positioned are carried to the sensing position 505 where they engage a shoe I98" and actuate switches 2G4 and 2U5 "c0ntrolling the motor 521 of a follow-up unit 528 whose driven shaft 529 is connected to the rack bar I94 through gears 530 so as to impart the follow-up motion to the switches. In this way, the shaft 529 is positioned angularly to indicator the previously computed present value of the target range. This value is compared with the actual present value by a difierential 53I having one terminal carried by the'shaft and the other terminal carrying a gear 532 which is driven through gears 533 to the gear I55 on-the present range indicator or shaft 2I.

The intermediate 534 of the diiferential 53! will thus be positioned angularly in accordance with the difference between the computed and actual values of the present range. This correction is added to or subtracted from the motion transmitted from the future range indicator 355 to the time of flight cam 434. To this end, the intermediate gear 534 meshes with a gear 535 on one terminal member of a difierential 535 having a gear 531 on its other terminal meshing with the last gear of the train 526 which is driven from the future range indicator or shaft 355. The intermediate gear 538 of the differential meshes with a gear 539 on the lower end of the shaft 420 which as previously described operates through the gearing 4 I8 and M9 to turn the time of flight and quadrant elevation cams 434 and 401.

Altitude correction.Referring now to Figs. 11 and 13, the rack bar I33 for positioning the future altitude setter I25 is actuated through gears 54!! from the shaft or future altitude indicator 355. This coordinate is thus recorded at the position 544 on the control lugs IIH of the chain 503. The lugs are advanced to the sensing position 555 where they act on the shoe I98 of the reader I and actuate switches 204 and 255 These switches control the motor 54I of a follow-up unit 542 to drive a shaft 543 which through gears 544 drives the rack bar I94 to position the switches and produce the follow-up action. The shaft 543 thus indicators the computed value of present altitude. This is compared with the actual value then set up on the present altiude indicator 23. To this end, a differential 546 has one terminal member fast on the shaft 543 and the other terminal shaft 541 carrying a gear 548 which through a gear 549 is driven from the intermediate 23 of the differential gearing BI which intermediate, as previously described, constitutes the present altitude indicator. The intermediate 55!! of the differential 546 is of course moved in one direction or the other away from a neutral position in accord;

ance with the differences between the computed and actual values of the present altitude, being disposed in such neutral position when these values coincide This will be the case when the target path is straight.

The altitude correction thus ascertained is added to or subtracted from the computed future altitude coordinate by means of a differential 55B one terminal of which carries a gear 552 meshing with the intermediate gear 550. The other terminal carries a gear 553 which through a gear 554 and the gear 545 is driven from the future altitude indicator 355. The intermediate gear 555 of the diiierential 55I meshes with the gear 439 which, as previously described, operates through the gears 425, 421, and 429 to drive the nut 424 by which the elevation and time of flight cams 491 and 434 are positioned axially.

It will be observed from the foregoing that the computed future coordinates are corrected continuously by the addition or subtraction of increments of theprcper sense and proportional in magnitude to the deviation of target coordinates in the present target position from the future coordinates computed for the present targetposition at a time lagging the present by exactly the time of flight corresponding to the present target position. Of course, if the target is traveling in a straight line and at uniform speed, all three of the computed and actual values of the present coordinates will be equal and no correction will be made assuming of course that no mechanical :OI' tracking errors'are made. As a result, the computed future target position thus corrected should coincide with the actual future position so that a hit should be 

